Atmospheric air, either indoors or outdoors, contains gaseous material and particulate matter. For example, air which is inhaled by human beings typically includes gases such as nitrogen, oxygen and carbon dioxide; water vapor, and particulate material which has dust, spores and the like.
A great deal of interest has developed in studying the nature, characteristics and quality of environmental air. In particular, there is great interest on the part of the Occupational Safety and Health Administration (OSHA) in studying indoor air quality. The quality of air in indoor settings, such as "white collar" office environments, is typically the subject of adverse claims by workers. There is also a good deal of interest in the study of indoor settings in homes as well as in other enclosed areas. The study of the indoor air quality in such settings can provide valuable information with regard to providing the effective ventilation and/or air circulation or recirculation within those enclosed areas. Such studies can also allow for the analysis of any contaminants found within those indoor environments so that steps may be taken to minimize such undesirable materials in order to improve the air quality.
Generally speaking, then, it is desirable to study environmental air in industrial areas such as factories, chemical plants and warehouses; in agricultural areas such as barns and silos; in social areas such as hotels, restaurants, bars, auditoriums and stores; and in personal areas such as homes and apartments and during travel. In particular, it is desirable to sample and analyze environmental air in such indoor spaces for asbestos fibers, dust, volatile organic compounds, pollen, coal dust, gasoline or diesel engine exhaust, smoke, wood stove exhaust or metal ions or material such as lead, beryllium, uranium, cadmium, zinc or selenium.
It is desirable to collect and analyze environmental atmospheric samples in a particular setting or settings over a fairly long period of time, such as a 24 hour period. However, for a realistic and representative assessment of the environmental air being sampled, it is useful to sample the particulate and vapor phases of the, for example, environmental tobacco smoke (ETS) aerosol, or other environmental material. Furthermore, it is desirable to utilize equipment which users can move along with them in different environments which the users may encounter during, for example, an 18-24 hour period. In order to be useful then, the sampling and collection system for environmental air samples should involve quiet, small and portable equipment such that it does not disturb the user while at the same time it dutifully monitors the user's environment. An air sampling system, such as the one disclosed herein, meets such requirements and provides a realistic and representative assessment of the particular indoor settings in which it is used because it is relatively unobtrusive and does not greatly affect human behavior during the sample collection periods.
It is, therefore, desirable to provide a portable, air sampling system which is capable of simultaneously monitoring both the particulate and vapor phases of, for example, ETS aerosol and which is capable of being easily moved by the user to other environments and used over a continuous period of time during which the sampling occurs. It is also desirable to utilize a simple yet effective system for calibrating such an air sampling system in order to ensure the accuracy of the sample collected by the air sampling system.
One approach to providing a portable air sampling device is disclosed in U.S. Pat. No. 4,786,472, which discloses a portable air sampling device in the shape of a briefcase. The components contained within the briefcase are capable of sampling air for analysis. For example, air is introduced into the briefcase through inlet ports and that air can be monitored for components of environmental tobacco smoke. Separate inlet ports are utilized to provide inlet air to a chemical collection device such as a sorbent tube for collecting nicotine and a filter for collecting respirable suspended particulate matter. In addition, a chemical detector for monitoring carbon monoxide levels and provisions for monitoring the environmental temperature and barometric pressure are also provided. Data is stored on a microcomputer within the briefcase for later transfer to a computer for data analysis.
Unlike the present invention, the device set forth in U.S. Pat. No. 4,786,472 requires the use of two pumps, one for each separate particulate and vapor phase collection and sampling system. The present invention, on the other hand, utilizes a single pump and collects both the particulate and vapor phases of the environmental tobacco smoke aerosol through a single manifold. Thus, the air sampling system of the present invention is very small and is therefore more easily transported by the user from place to place within his personal environment. In addition, the present system will run for longer time periods than that discussed in U.S. Pat. No. 4,786,472. A novel system for calibrating the air sampling system of the present invention is also provided.
Another approach to a portable air sampler is disclosed in U.S. Pat. No. 4,569,235, which discloses a sequential air sampler assembled within a portable industrial housing which allows the air sampler to operate by either battery or line power. The system disclosed in U.S. Pat. No. 4,569,235 utilizes a plurality of components through which air samples are sequentially drawn utilizing a single pump and a flow rate control system. However, the system disclosed in U.S. Pat. No. 4,569,235, by utilizing a single vacuum pump, does not simultaneously sample environmental air for particulate and vapor phases of environmental tobacco smoke aerosol, nor is that system "portable", in other than the industrial sense of that word.
Yet another approach to an air sampling device which is used for sampling tobacco smoke in public places is disclosed in the Apr. 17, 1975 issue of the New England Journal of Medicine, Vol. 292, pages 844-845, in an article entitled "Concentrations of Nicotine and Tobacco Smoke in Public Places", by Hinds et al. That article discloses, in FIG. 1, a sampling system which utilizes a pump which is used to draw air through a filter and is directed to the measurement of only the particulate phase of tobacco smoke. While disclosing a portable air sampling system, the sampling system of Hinds et al. is not capable of simultaneously collecting particulate and vapor phase samples of environmental tobacco smoke aerosol.